Discrete optoelectronic devices have recently become the key to optical telecommunications, data processing and sensing systems. To meet today's stringent requirements for information transmission and processing capacity, optoelectronic devices need to be configured to provide higher performance, particularly with regards to reliability, than those in the past. At the same time, however, the devices should maintain their relatively low manufacturing cost.
Optoelectronic integrated circuits are thin-film type integrated circuits that integrate multiple optical and electronic components on a single substrate. Through such integration, a more compact, stable and functional optoelectronic system can be produced. Optoelectronic integrated circuits typically integrate laser diode light sources, switches/modulators/couplers, interconnecting waveguides and photodiode detectors, along with traditional electronic integrated components, on a common substrate.
The integration of lasers and photo detectors with other optical signal processing circuits, by the use of waveguides, produces useful components that embody advanced optical signal processing functions. The integration of waveguides in circuits using semiconductor or dielectric materials is typically referred to as integrated optics or optical integrated circuits. More recent integration of various waveguide-based devices and optoelectronic conversion devices on a common substrate, is typically referred to as photonic integrated circuits.
The integration of optoelectronic devices with electronic circuits on a single substrate has many advantages. For instance, it typically reduces parasitic resistance that occurs between electrical interconnections. Furthermore, the number of fiber optic elements and interconnections can be reduced by monolithic integration of optoelectronic components. This enables integrated circuits to be manufactured with improved compactness as well as improved speed and noise characteristics. Among others, these advantages make optoelectronic integrated circuits useful in very high-speed telecommunications and coherent optical telecommunications systems.
The use of optoelectronic integrated circuits does, however, have certain requirements. One of those requirements is the need for easily and inexpensively manufacturing the integrated waveguide required to couple the various optical devices of the optoelectronic integrated circuit. Presently, virtually all known methods for manufacturing the integrated waveguides require the use of photolithographic masks to define the waveguide. For example, in one well-known process, a photolithographic mask is used to control the diffusion of gas/ion particles (i.e., what eventually forms the waveguide) into a substrate. In another well-known process, the photolithographic mask is used to pattern a material, which is eventually diffused into the substrate to form the waveguide. Accordingly, in virtually all known methods for manufacturing the integrated waveguide, a photolithographic mask is used.
The process described above for forming the integrated waveguides is an expensive process. Much of the expense arises from the specialized tools required to form such waveguides. However, much of the expense also arises from the required use of photolithography. As those skilled in the art readily understand, manufacturing photolithographic masks is a very expensive process. This, combined with the inability to retrofit existing masks for a new process flow or device, results in an extremely expensive technique.
A need therefore exists in the art for a method of manufacturing a waveguide that does not experience the drawbacks associated with the prior art methods.